The invention relates generically to a device for relieving pressure during a failure in the containment of a nuclear power station comprising a pressurized water reactor or boiling water reactor, the stream of compressed air from the containment being filtered and discharged to the atmosphere, the device comprising a filter unit for filtering off radioactively contaminated substances entrained in the stream of compressed air, and duct systems and fittings connecting the filter elements of the filter unit. As is known, the containment of a nuclear power station is a building designed to safety regulations and surrounding the reactor vessel and consequently the reactor core. In the invention, the term "filter unit" denotes the functional combination of a number of filter elements, even if serving widely different purposes. In the invention, a "duct system" can comprise a single duct or number of ducts connected by fittings.
The generic device is known from the recommendations of the Reactor Safety Commission. It is included among the measures for protection against failures inside the station and serves to reduce the remaining risk, more particularly during a meltdown. In the known device, the filter unit and all the elements thereof are disposed outside the containment. This necessitates special, expensive buildings for the filter unit, particularly since the filter elements absorb radioactive substances during use and accordingly have to be screened. There are also functional problems. Unless further modifications are made to the building in which the filter unit is located, the filter elements will be in an environment at a temperature considerably lower than the temperature in the containment. A disturbing amount of radioactively contaminated condensate therefore collects in the filter elements. The condensate lowers the efficiency of the filter elements.
It is the object of the invention to improve the generic device so that the buildings can be considerably less expensive and so that the amount of condensate collecting in the filter elements can be reduced, so as not to impair the efficiency of the filter elements through a disturbing accumulation of condensate.